1. Field of the Invention
The present invention relates to a variable digital phase-shifter and more particularly to a digital velocity corrector for a video recorder in which a phase-shifter of this type is employed.
2. Description of the Prior Art
In video recorders, a velocity corrector has the function of correcting the phase error produced between the temporal reference of the recorded video signal and the temporal reference of the corresponding video signal which has been delivered by the camera equipment. Velocity correctors of known types either call for the use of purely analog solutions in which phase lags are compensated by delay lines or else they make use of hybrid devices which operate in both digital and analog modes and in which provision is made for a sampling clock phase-modulated as a function of the phase error produced between the temporal references of the recorded video signal and the corresponding video signal which has been delivered by the camera equipment.
In either of the two alternatives just mentioned, the delay lines employed and the voltage-controlled oscillators which permit phase-modulation of the sampling signal entail the need for adjustments and result in a non-negligible increase in price of video recorders which incorporate velocity correctors of the type mentioned in the foregoing. Solutions to these drawbacks can undoubtedly be found by making use of entirely digital phase-correcting devices, but these solutions still carry a heavy cost penalty, mainly by reason of the large number of numerical operators required for their practical application.